The present invention relates to a new and improved primary surface for use in a corrugated plate type heat exchanger, and more particularly a heat exchanger device made up of a plurality of identical plates of relatively thin material, so formed and stacked as to provide heat transfer through the plates to and from a series of alternate flow passages formed between the stacked, alternate plates.
U.S. Pat. No. 3,424,240 to Stein et al., assigned to the assignee of the present invention, discloses a heat exchanger device made up of a plurality of plates formed in two types of configurations stacked alternately in pairs to form the stack. The two types of plates have spaced openings therethrough which are aligned when stacked to form inlet and outlets to and from one of the series of longitudinal flow passages in the stacked plates. The first type of plates is preferrably formed with a pattern of corrugations between the spaced openings extending across the plates in a radially outward direction thus providing channel forming, generally parallel wave formations on both surfaces thereof. On the other hand, the other of the two types of plates is formed with a pattern of generally parallel corrugations extending circumferentially along the plates between the spaced openings therethrough, the pattern of corrugations on the second type of plates extending transversely to the corrugations provided on the first type of plates when the two different types of plates are positioned adjacent one another to form a construction pair with the spaced openings in alignment. The aligned openings in the first and second types of plates are sealed together by welding or brazing.
One of the drawbacks in making the plates is that it is necessary that two different sets of dies be utilized for forming the two different types of plates. In order to avoid this difficulty, a "Stacked-Plate Heat Exchanger made of Identical Corrugated Plates" is disclosed in co-pending U.S. patent application Ser. No. 312,309, filed Oct. 16, 1981, by John J. Martin, and assigned to the assignee of the present invention, the entire disclosure of which is hereby incorporated by reference. Disclosed therein is a corrugated stacked-plate heat exchanger which employs identical plates each of which is configured so as to include about the radially outer portion thereof an alternating arrangement of radially extending and transversely extending parallel corrugations. Since the plates are identical and of uniform thickness, the internal stresses in the structure due to the expansion and contraction of the metal plates during a wide range of temperature variations are limited. The resulting corrugated stacked-plate heat exchanger obviates the need for tubular inlet and outlet channels extending longitudinally through the stack and the necessity for connections and inlet and outlet openings from such tubes to and from the heat transfer channels in the stack. Furthermore, the provision of identical plates employed in the heat exchanger facilitates the assembly of the heat exchanger since only a single hydroform punch is required and die upkeep is thus minimized. Continuous production of identical plates is available since the die does not have to be changed, as was required to manufacture the series one and series two plates in the heat exchanger of U.S. Pat. No. 3,424,240.
Although the use of the single type of plate in the above-mentioned Ser. No. 312,309 reduces construction costs and system complexity, many of the operating characteristics inherent in the prior heat exchangers, such as that disclosed in U.S. Pat. No. 3,424,240 are also inherent in the newer heat exchanger. When the first and second types of plates are placed adjacent each other, a grid of touching points is formed between each pair of adjacent plates by the intersection of the longitudinal and transverse ridges from the alternate plates. A plurality of flow passages through which a gas or air travels are established between the touching points on the grid. When so formed, however, a contraction and expansion of the flow passage at each transverse ridge is inherently produced, the flow passages varying in area along the direction of flow to thereby promote thermal mixing within the passages and enhance the rate of heat transfer.
However, by reducing the pressure losses associated with expanding and contracting passages, a primary surface heat exchanger may achieve a higher ratio of heat transfer parameter to friction factor.